FIELD OF THE INVENTION
The invention is based on a fuel delivery pump for a fuel injection pump for internal combustion engines.
EP 0 166 995 B1 has disclosed a fuel delivery pump of this kind embodied as a gear delivery pump, which feeds the fuel from a storage tank into the intake chamber of a fuel injection pump. To that end, the delivery pump has a pair of gears that mesh with external engagement, which delivers fuel from an intake chamber connected to the storage tank via an intake line, into a pressure chamber connected to the intake chamber of the fuel injection pump via a supply line. To control the pressure in the pressure chamber or the feed quantity to the fuel injection pump, a bypass conduit is provided between the pressure chamber and the intake chamber of the fuel delivery pump. The opening of this bypass conduit is carried out by means of a pressure valve inserted in the bypass conduit, which valve unblocks a particular opening cross section as a function of the spring force of the valve spring when there is a particular pressure difference between the pressure chamber and the intake chamber. The opening time of the pressure valve can be set via the initial force of the valve spring, which is why the axial position of the abutment of the pressure valve spring can be adjusted.
The known fuel delivery pump, however, has the disadvantage that the bypass conduit that contains the pressure valve is disposed outside the delivery pump or spatially speaking, relatively far from the gear pair, which results in an increase in construction and assembly costs as well as taking up a lot of space.
The German Patent Application P 44 41 505.2 has disclosed a fuel delivery pump which avoids the above mentioned disadvantages. The bypass conduit that contains the pressure valve is integrated into the housing of the delivery pump so that no additional space is required. This known fuel delivery pump, though, has the disadvantage that when an engine is operating, the fuel quantity delivered is significantly higher than the fuel quantity required. The excess fuel quantity delivered is routed via the bypass valve from the pressure chamber into the intake chamber and as a result of the pressure drop thus produced at the valve, the energy is converted into heat, which produces a loss in operating power.